People who migrate from developing countries to the industrial world usually trade one set of health problems for another. This becomes startlingly clear in a new study showing that many Asian immigrants in Canada develop high blood pressure within a few years after arriving.

The saying "When in Rome, do as the Romans do" speaks of assimilating into a new culture. But assimilating can mean adopting the bad along with the good. In just such an example, a new study shows that Asian migrants to Canada are taking up the Western lifestyle both to their detriment as well as their benefit.

Researchers at Portland State University in the U.S. state of Oregon determined this by examining 1997 Canadian government data on nearly 2,000 Asian immigrants. Portland State University public health specialist Mark Kaplan says they found that the Asians smoke less than their peers who stayed home, but also tend to develop high blood pressure the longer they live in North America.

"When you look at recent arrivals, Asian immigrants who have been in Canada just zero to four years, the rate of hypertension was under three percent," he said. "It was for the general population at the same time 10 percent. But by 10 years, that prevalence rate increased four-fold, suggesting that over time, the disease patterns of the immigrant groups begins to mimic that of the dominant culture."

Mr. Kaplan's research appears in the Journal of Epidemiology and Community Health. It is the latest of several studies showing that immigrants to the West have higher rates of heart disease and related risk factors like hypertension and obesity than their counterparts back home.

"This study is a typical pattern that we're seeing now among immigrants," said Barbara Krimgold of the Center for the Advancement of Public Health, a health policy research organization in Washington. "Immigrants tend to be in neighborhoods with, say, lots more advertising of alcohol, lots more fast food, less access to fresh fruits and vegetables."

Another recent study looked at the weight increase in the children of Mayan families who emigrated to the United States in the 1980s after fleeing civil war and persecution in Guatemala. University of Michigan anthropologist Barry Bogin found these émigré youngsters taller than their Guatemalan peers, but also fatter.

"The greater average height and longer legs of Maya-American children indicate better health," he said. "But an alarming number of Maya-American children exhibit weight problems. We find that nearly half are overweight and 42 percent of all the Mayan-American children are obese."

Mr. Bogin and Mr. Kaplan do not dismiss the idea that these ethnic groups may be genetically predisposed toward the health problems they encounter in the West. But Mr. Kaplan suggests the decisive factor is their adoption of the more sedentary Western lifestyle and higher fat diet. Barry Bogin agrees.

"In the Mayan-American kids I've studied, this is happening within a generation," he said. "Some of these children are born in Guatemala, their families come here, and they still become obese. So there may be a propensity in some for more individuals to be susceptible toward obesity, but this is happening to everyone and it's happening too fast to be genetic or evolutionary, as some others have claimed."

Mark Kaplan says immigrants' new, less healthy lifestyles present challenges to health policy makers with limited resources in ethnically diverse societies. In the case of the Asians in his study, for example, he suggests directing health awareness programs at those who have lived in North America the longest, since the research shows they have the highest blood pressure.

"There is a lot of mobility around the world," he said. "So the question is, how do we design public health programs that effectively target those immigrant groups who are at greatest risk?"